Transcript Central Nervous System

 Ectodermal
tissue (embryonic) folds
creating neural tube.
 This neural fold tissue creates the
brain (anterior fold) and the spinal
cord (posterior fold)
 Anterior fold grows quicker than
posterior producing:
Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hind brain)
 Prosencephalon
1- Telencephalon
- Cerebrum (cerebral cortex,
white matter and basal nuclei)
2- Diencephalon
- (thalamus and hypothalamus)
 Mesencephalon
- Brain stem (midbrain)
 Rhombencephalon
1- Metencephalon
-Brain stem (pons) and
Cerebellum
2- Myelencephalon
- Brain stem (medulla
oblongata)
 Hollow
spaces in the brain termed
ventricles.
CSF is produced and circulated (lined
with ependymal cells)
Lateral ventricles (2) separated by a
thin membrane called the septum
pellucidum. (CSF produced in the
choroid plexus)
Each lateral ventricle communicates
with the third ventricle via a channel
called an interventricular foramen
(foramen of Monro)
Third ventricle is continuous with the
fourth ventricle via the cerebral
aquaduct of Sylvius
Fourth ventricle drains CSF into spinal
cord through the foramen of
Magendie.
Cerebral Hemispheres
Superior part of the brain
 Covered entirely by ridges (gyri),
separated by shallow grooves (sulci) and
deeper called grooves (fissures)
 Anatomical landmarks:

– Longitudinal fissure
– Frontal, parietal, occipital, and temporal lobes
 Deep
to temporal, parietal, and frontal lobes is a fifth
lobe called the insula
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Central sulcus of Rolando
Pre/post central gyri
Lateral sulcus of Sylvius
Calcarine sulcus
Parito-occipital sulcus
Transverse cerebral fissure
Cerebral Cortex:
Seat of consciousness.
 Cerebral cortex contains three functional
areas:
1- Motor areas - control voluntary motor
function
2- Sensory areas - provide for conscious
awareness of sensation
3- Association areas - integrate all other
information
Each hemisphere is concerned with the
sensory and motor functions of the
opposite side of the body
Motor regions are located in the posterior
frontal lobe.
 Primary motor cortex - precentral
gyrus in the frontal lobe
- Large neurons (pyramidal cells) allow
conscious control of movement of
skeletal muscles
-The pyramidal cells' long axons from
voluntary motor tracts called pyramidal
(corticospinal) tracts
-Motor areas have been spatially
mapped = somatotropy. (Homunculis)
 Premotor
cortex - anterior to the
precentral gyrus in the frontal lobe.
Regions controls learned motor skills
that are repeated or patterned.
Also coordinates the movements of
muscles simultaneously and\or
sequentially by sending activating
impulses to the primary motor
cortex.

Broca's area - anterior to the premotor
area
- Involved in directing motor speech.

Frontal eye field - anterior to the
premotor cortex and superior to Broca's
area
Controls voluntary movement of eyes.
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Sensory Areas (parietal, temporal, and
occipital lobes)
Primary somatosensory cortex postcentral gyrus of parietal lobe
(immediately behind primary motor
cortex)
– Neurons receive info (from sensory receptors,
skin, and muscles) and identifies body region
being stimulated

Somatosensory association area - lies
posterior to the primary somatosensory
cortex
– Integrate and analyze somatic sensory inputs
(e.g. temperature and pressure) into
comprehensive evaluation.
 Visual
areas - occipital lobes
contain primary visual cortex
(receive information from retina) and
visual association area (interprets
information from retina).
 Auditory
areas - temporal lobes
contain primary auditory cortex
(receives impulses from inner ear)
and auditory association area
(interprets sound).
 Olfactory
cortex - temporal lobe in
region called the uncus; enables
conscious awareness of odors.
“Skunkus in my uncus”
 Gustatory
cortex - parietal lobe
deep to temporal lobe; involved in
perception of taste.
Cerebral Cortex
 Association
Areas
 Somatosensory cortex - posterior to
the primary somatosensory cortex
– The association areas, in turn,
communicate with the motor cortex and
with other sensory association areas to
analyze, recognize, and act on sensory
inputs.
 Prefrontal
cortex - anterior portions
of frontal lobe
- Involved with intellect and complex
learning (cognition) and personality
- Tumors may lead to personality
disorders - prefrontal lobotomy are
performed in severe cases of mental
illness.
Alzheimer’s Disease
 Language
areas - found in
Wernicke's area of temporal lobe of
one hemisphere (usually left)
- Involved in interpretation of
language.
 Cerebral
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White Matter:
Responsible for communication
within the brain between each
hemisphere, cerebral cortex and
lower CNS centers.
White matter bundled into large
tracts
Fibers and tracts are classified
according to the direction in which
they run.
Commissural
- Connects the gray areas of both
hemispheres so the brain functions as one
unit
- Corpus callosum: superior to the lateral
ventricles
- Fibers run horizontal
Association fibers:
- Connect within the same hemisphere.
- Connects adjacent gyri and different lobes.
- Fibers run horizontal
Projection fibers:
- Connects cortex to lower brain
centers (spinal cord and brain stem).
- Fibers run vertical
- Internal capsule and corona radiata
Basal nuclei: (cell bodies) ganglia:
Receive extensive input from the entire
cerebral cortex and project messages
(via relays) to the premotor and
prefrontal cortices
Amygdala: hangs off of the tail of the
caudate nucleus. Center for fear.
 Diencephalon
(thalamus,
hypothalamus)
 Thalamus:
- Gray matter areas enclose the third
ventricle.
- Receive and projects fibers from the
cerebral cortex.
- All senses (afferent) from the body
will pass through the thalamus (relay
center). Senses are then sorted out
- Gateway to the cerebral cortex
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Hypothalamus:
Walls of hypothalamus (tissue) meet and
extend, forming infundibulum (stalk),
connecting the pituitary to base of
hypothalamus.
The hypothalamus is the main visceral
control center of the body.
Homeostatic roles:
1- Autonomic control center - regulates
involuntary nervous system activity
(influences BP, HR, GI motility,
Respiration rate and depth, and pupil
size).
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2- Center for emotional response and
behavior - numerous connections
with cortical association areas
(initiates physical expressions of
emotion).
3- Body temperature regulation hypothalamus neurons monitor blood
temperature flowing through
hypothalamus (initiates sweating,
shivering, etc.).
4- Regulation of food intake - responds
to hormones and blood levels of
nutrients. (hunger; satiation)
5- Regulation of water balance and
thirst - triggers ADH release, causing
kidneys to retain water; thirst
centers stimulated, cause us to
drink.
6- Sleep-wake cycle regulation - set
timing of our sleep cycle in response
to daylight-darkness cues.
7- Control of endocrine system hypothalamus produces releasing
hormones that control the secretion
of anterior pituitary hormones
 Brainstem:
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Gray matter surrounded by white
matter
Controls automatic functions
necessary for survival (cardiac,
breathing, digestion, head and eye
movement)
Composed of the
- midbrain
- pons
- medulla oblongata
Midbrain:
Structures:
Cerebral peduncles - pyramidal motor tracts
descending toward spinal cord.
Cerebral aqueduct - connect 3rd and 4th
ventricle, enclosed by nuclei
Nuclei - corpora quadragemina (two pair)

– Superior colliculi (visual reflex, head/eye
movement)
– Inferior colliculi (auditory relay, startle reflex)
Also embedded in white matter of midbrain
are two pigmented nuclei Substantia nigra
(site of dopamine production)
and red nucleus (contains iron &
hemoglobin and coordinates muscular
movements: limb flexion).
Classes of Neurotransmitters:
 Acetylcholine: excitatory (skeletal muscle)
 Biogenic amines
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– Dopamine, Norepinephrine, and epinephrine
(feel good catecholamines)
– Serotonin: inhibitory
– Histamine
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Amino acids
– GABA (gamma-aminobutyric acid) (inhibitory)
– Glutamate: excitatory
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Peptides
– Endorphins and enkephalins: inhibitory
(opioids)
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Pons:
between midbrain and medulla
oblongata
Conduction pathway between higher
and lower brain centers
Middle cerebellar peduncles connect
pons with the cerebellum
Some pons nuclei (pneumotaxic) are
respiratory centers that help
maintain normal rhythm of
breathing.
Medulla Oblongata:
- most inferior part of brain stem, blends
into spinal cord at the level of the foramen
magnum.
Structures:
- Pyramids - pyramidal tracts descending
from motor cortex
- Decussation of pyramids - fibers of
pyramids cross over at one point;
supporting that each hemisphere controls
voluntary muscles
- Olives - lateral to pyramids, relay
sensory information on the state of stretch
of our muscles and joints to the
cerebellum
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Medulla oblongata contains visceral
motor nuclei that control:
1- Force and rate of heart contraction
2- Regulate BP (by regulating smooth
muscle respiratory contraction)
3- Rate and depth of breathing,
therefore maintain respiratory
rhythm
4- Vomiting, hiccupping, swallowing,
coughing, and sneezing
 Cerebellum:
“little brain”.
Processes inputs from the cerebral
motor cortex, brainstem nuclei, and
sensory receptors to provide precise
timing and patterns of skeletal
muscle contraction. Coordinated
movements such as driving and
playing the piano. Controls
equilibrium.
- Composed of two cerebellar
hemispheres connected by the
vermis
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Transverse gyri (pleated) called folia.
Pattern of white matter inside resembles a
branching tree; arbor vitae.
Contains posterior and anterior lobes that
regulate subconscious skeletal.
Cerebellar Processing:
1- Initiates voluntary muscle contraction
2- Determines body orientation (body
parts in space)
3- Coordinates forces, direction, extent of
muscle contraction
Cerebellum
 Limbic
system:
Complex group of fiber tracts that
form a ring around the brainstem
Part of the brain that is associated
with emotions, pleasure, pain, fear,
memory, anger, rage, sorrow and
sex drive.
Smell is tied in with memory
Amygdala: fear
Hippocampus: memory
 Meninges
(PAD): connective tissue
that covers the brain and spinal cord
1- Pia mater: contacts brain surface
and is found within the fissures and
sulci
2- Arachnoid: separated from pia
mater by subarachnoid space
3- Dura mater (tough mother): double
membrane surrounding brain.
A- Periosteal layer - attached to skull
B- Meningeal layer - deep to
periosteal, outermost brain covering;
extends inward to form flat septa
that anchor brain to skull:
– Falx cerebri (in longitudinal fissure)
– Falx cerebelli (runs along vermis of
cerebellum)
– Tentorium cerebelli (in transverse
fissure)
Spinal Cord: runs through the vertebral
foramen.
Begins at the foramen magnum and ends at
the level of L2.
- Cervical and lumbar enlargements
- Anterior median fissure and posterior
median sulcus
- Conus medullaris (L1-L2), cauda equina,
and filum terminale
- 31 pairs of nerves each two points of
attachment called roots (dorsal and
ventral)

Spinal Cord Anatomy
Lumbar Puncture (LP)
 Posterior/dorsal
root containing
sensory nerve fibers -includes a
swelling (ganglion) containing cell
bodies of sensory neurons (dorsal
root ganglion)
 Anterior/ventral root containing
motor nerve fibers
- Interior gray matter (cell bodies)
surrounded by white matter (myelinated
neurons)
- Central canal (continuous with the fourth
canal)
- Gray matter divided into horns: anterior,
posterior, and lateral
- White matter divided into columns:
anterior, posterior, and lateral
- Each white column contains bundles of
nerve axons (called tracts) having a
common origin or destination
- Two types of tracts: ascending (sensory)
and descending (motor)
 Major
spinal cord tracts:
Corticospinal: descending motor tract
that transmits motor impulse from
cerebral cortex down spinal cord out
to skeletal muscle
Spinothalamic: ascending sensory
tract that transmits pain,
temperature and deep pressure.
Spina Bifida